Mars soil offers clues to the past

Dec. 3, 2012
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A true-color panorama taken by the Curiosity rover on Mars. / NASA/JPL-Caltech/Malin Space Science Systems

by Dan Vergano, USA TODAY

by Dan Vergano, USA TODAY

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No Martians have been found, but scientists controlling NASA's Curiosity rover reported Monday that its first soil sample from Mars contains tantalizing but unproven hints of chemicals essential to life.

NASA landed the $2.5 billion rover on Mars in August on a mission to search for signs of chemistry indicating whether conditions for life once existed or still exist there. The soil sample results reported Monday at the American Geophysical Union meeting in San Francisco contain hints of "organic" chemicals essential to biochemistry, but the rover team said more analysis is needed.

"We just don't know if these are indigenous to Mars, and it is going to take some time to work through," said mission chief scientist John Grotzinger of Caltech. The organic carbon-based compounds could be earthly contamination from the sampling instruments or from meteorite dust, rather than truly from Mars. Determining whether these compounds represent "some kind of biological material is well down the road for us," he added.

The traces of organic chemicals reported by the rover's instruments likely are ones cooked up in the analysis itself and are not truly native to Martian soil, cautioned biochemist Jeffrey Bada of the Scripps Institution of Oceanography at the University of California-San Diego. "It is good that they are being appropriately cautious about the results," said Bada, who is not part of the rover team. "The real triumph is we have a very complicated chemistry-analysis-instrument working perfectly on another planet, a remarkable feat."

A sandpit called Rocknest served up the first soil sample, its dirt largely made of iron minerals typical of the fine Martian dust coating the Red Planet. "It's finer than sugar, but coarser than flour," said mission imaging scientist Ken Edgett of Malin Space Systems in San Diego.

The soil sample also contained chlorine-laced compounds similar to ones observed on the Red Planet's frozen poles by NASA's now-defunct Phoenix lander in 2008.

Speculation of dramatic chemistry results that preceded Monday's presentation led NASA's Jet Propulsion Laboratory, which manages the rover, to issue a news release in advance, downplaying the results.

Since arriving in August in a dramatic landing on a former riverbed, the nuclear-powered rover has traveled nearly 1,700 feet from its landing site inside the 96-mile-wide Gale Crater on Mars. The rover is now stationed near a rock it will inspect with a drill this week, another first for a Mars rover.

Within a year, the rover will travel to apparent clay formations ringing Aeolis Mons, or Mount Sharp, a mountain that rises 3.4 miles above the floor of the crater. Thought to be several billion years old, these layers of clay are seen as the likeliest places to hide leftover complex organic chemicals from when Mars experienced wetter and warmer weather.